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Tonsillar Herniation Extending More Than 5 Mm Below the Foramen Magnum on MR Imaging of the Head Is 0.78% (36)

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Tonsillar Herniation Extending More Than 5 Mm Below the Foramen Magnum on MR Imaging of the Head Is 0.78% (36) Surgical Experience in Pediatric Patients with Chiari I malformations age ≤ 18 years Submitted for MCh Neurosurgery By Dr. Vipin Kumar October - 2012 Department of Neurosurgery Sree Chitra Tirunal Institute for Medical Sciences & Technology Thiruvananthapuram – 695011 1 Surgical Experience in Pediatric Patients with Chiari I malformations age ≤ 18 years Submitted by : Dr. Vipin Kumar Programme : MCh Neurosurgery Month & year of submission : October, 2012 2 CERTIFICATE This is to certify that the thesis entitled ―Surgical experience in pediatric patients with Chiari I malformations age ≤ 18 years‖ is a bonafide work of Dr. Vipin Kumar and was conducted in the Department of Neurosurgery, Sree Chitra Tirunal Institute for Medical Sciences & Technology, Thiruvananthapuram (SCTIMST), under my guidance and supervision. Dr. Suresh Nair Professor and Head Department of Neurosurgery SCTIMST, Thiruvananthapuram 3 DECLARATION This thesis titled “Surgical experience in pediatric patients with Chiari I malformations age ≤ 18 years ” is a consolidated report based on a bonafide study of the period from January 1999 to June 2011, done by me under the Department of Neurosurgery, Sree Chitra Tirunal Institute for Medical Sciences & Technology, Thiruvananthapuram. This thesis is submitted to SCTIMST in partial fulfillment of rules and regulations of MCh Neurosurgery examination. Dr. Vipin Kumar Department of Neurosurgery, SCTIMST, Thiruvananthapuram. 4 ACKNOWLEDGEMENT The guidance of Dr. Suresh Nair, Professor and Head of the Department of Neurosurgery, has been invaluable and I am extremely grateful and indebted for his contributions and suggestions, which were of invaluable help during the entire work. He will always be a constant source of inspiration to me. I owe a deep sense of gratitude to Dr. Girish Menon for his invaluable advice, encouragement and guidance, without which this work would not have been possible. The critical remarks, suggestions of Dr. Gopalakrishnan C. V, helped me in achieving a high standard of work. I am deeply indebted to Dr. Mathew Abraham, Dr. Easwer H. V, Dr. Krishnakumar K, Dr. George Vilanilam, Dr. Jayanand Sudhir and thank them for their constant encouragement and support. Last but not the least, I owe a deep sense of gratitude to all my patients without whom this work would not have been possible. 5 INDEX INTRODUCTION 7-10 REVIEW OF LITERATURE 11-69 AIMS AND OBJECTIVES 70 MATERIALS AND METHODS 71 RESULTS 72-87 DISCUSSION 88-99 CONCLUSIONS 100 REFERENCES 101-106 PROFORMA 107-108 6 INTRODUCTION Chiari malformation Type I is characterized by caudal descent of cerebellar tonsils and may or may not be associated with the presence of a syrinx, a degree of medullary descent and buckling of the lower medulla may also be present. Herniation of the tonsils more than 5 mm below the foramen magnum on MR imaging is considered diagnostic in adults (1). Mikulis DJ. Et al - criteria for ectopia of the cerebellar tonsils: 1st decade of life, 6 mm; 2nd and 3rd decades, 5 mm; 4th to 8th decades, 4 mm; and 9th decade, 3 mm (40). It is more common in women, with a female-to-male ratio variably reported as 3:1 to 1:1 (28, 39). In pediatric chiari I malformation female-to-male ratio variably reported as 1.5:1 to 1:1.5 (20, 27, 59). If only patients with Chiari I malformation associated with syringomyelia are included, the female-to- male ratio ranges from 1:1 to 1.3 (29). The reported prevelance of tonsillar herniation extending more than 5 mm below the foramen magnum on MR imaging of the head is 0.78% (36). Some patients with this malformation are completely asymptomatic, and the diagnosis is established incidentally when MRI is performed for some other reason. Clinical manifestations – Headache common symptom of pediatric Chiari I malformation, is found in 40 – 60 % of patients (15, 27, 59, 61). 7 It is described as a heavy, crushing, or pressure-like sensation at the back of the head that radiates to the vertex, behind the eyes and to the neck and shoulders which accentuated by physical exertion and by Valsalva maneuvers (e.g., coughing, sneezing, or vomiting). Most patients also experience ocular disturbances, such as blurred vision, photophobia, diplopia, and visual field deficits. However, the neuro- ophthalmological examination in these patients usually is normal. 10 -21 % patients report a lower cranial nerve (15, 27, 59,). The most common symptoms in this group are dysphagia, sleep apnea, dysarthria, hoarseness. Syrinx reported in pediatric chiari I malformation ranges from 51 -72 % (27, 59, 61, 43, 44, 47, 48). The patients with syringomyelia more frequently suffered motor deficits than those without syringomyelia (ratio 7:1). Sensory symptoms were also more frequent in this group (ratio 4:1) (27). Associated diagnoses with pediatric chiari I malformation reported are hydrocephalus - 11%, type I neurofibromatosis -5.5%, idiopathic growth hormone deficiency - 5.5%, Klippel–Feil anomaly - 5%, basilar invagination - 4% and Sprengel deformity - 2.7% (59, 61). The diagnosis of Chiari I malformation is suspected when analyzing the clinical course and physical examination, but it must be confirmed with imaging studies. MRI is considered the 8 most important study for establishing the diagnosis and planning the surgical treatment. A T1-weighted sagittal view of the CVJ usually shows both the tonsillar herniation and syringomyelia, but in patients with small spinal cord cavities, T2- weighted imaging also can be very helpful. MRI also is useful for identifying other related anomalies, such as tumors and CVJ problems. Dynamic MRI helps demonstrate abnormalities in CSF flow at the foramen magnum and the benefits of decompressive surgery in patients with the Chiari I malformation (57). Ultrasonography is another useful study in Chiari I malformation with mild Tonsillar herniation (rostral to C1), but it is used only during surgery to identify when the CSF circulation has been re-established during the procedure (34). The management strategy follows a ―top down‖ rule (15, 42, 53, 58). This implies that one proceeds from the cranial to caudal direction. If there is hydrocephalus it is dealt with first by ventriculoperitoneal shunt or other appropriate shunting technique. If the shunting does not ameliorate the symptoms then foramen magnum decompression with a lax expansive duroplasty is done to deal with the impaction of tonsils into the upper cervical canal. The expansile duroplasty allows more room around the foramen magnum and opens the subarachnoid pathways. If with this manoeuvre the syrinx cavity 9 resolves or flow disappears then there is no need for further intervention. If the syrinx persists then one would consider direct shunting of the syrinx. With the natural history known incompletely, poorest prognosis is seen in patients with central cord signs; the best prognosis is found in patients with paroxysmal intracranial hypertension (62). Saez et al (63) classify patients into preoperative prognostic categories revealed that more than 80% of patients with paroxysmal intracranial hypertension or cerebellar dysfunction achieved a favorable outcome, that 65% of patients with foramen magnum compression improved, and that only 33% of patients with central cord disturbance improved. 10 REVIEW OF LITERATURE HISTORY: Chiari malformations encompass a spectrum of congenital hindbrain herniation syndromes. First described by the Austrian pathologist Hans Chiari in 1891 (11). His work on type I Chiari malformation (CIM) was published in Deutcsche Medizinische Wochenscriff. He described a 17- year-old girl who suffered from hydrocephalus but did not have symptoms attributable to the cerebellum or medulla. The patient died of typhoid fever. At autopsy, Chiari discovered an ―elongation of the tonsils and medial parts of the inferior lobes of the cerebellum into cone- shaped projections, which accompany the medulla oblongata into the spinal canal.‖ Five years later, Chiari described 14 similar cases, noting that the grade of hydrocephalus was not related to the severity of the craniospinal changes. He theorized that an additional mechanism might play a role in this condition, such as insufficient bone growth and insufficient enlargement of skull parts, resulting in increased intracranial pressure. Briefly a few of the relevant historical vignettes in the description of this disease has been mentioned below : 1. 1901 First description of CIM-related neurological symptoms, by Home´n (22) 11 2. 1935 Russell and Donald (64) suggested that hydrocephalus could be secondary to the cranio-cervical deformity and could be treated by decompressing the foramen magnum. They also introduced the notion of Chiari malformation in the English-language literature; 3. 1938 McConnell and Parker (35) described the first adult patients with CIM (and hydrocephalus); they also used the term ‗‗tonsils‘‘ to indicate the prolapsed portion of the cerebellum. The same year, Aring (5) reported on the first case of CIM without hydrocephalus; 4. 1941 First radiological diagnosis of CIM, realized by Adams, Schatzki and Scoville (2). The authors reported on a patient with a ‗‗block‘‘ at the level of C3 on preoperative myelography. The authors also classified the symptoms of CIM into 5 groups: (a) Raised intracranial pressure, (b) Cranial nerve palsy, (c) Brainstem compression, (d) Spinal cord compression, (e) Cerebellar signs Regarding history of management of chiari I malformation : Gardner (19) did decompression of the foramen magnum and atlas with opening of the fourth ventricle and plugging of the obex. 12 Williams (67) modified this technique by suturing muscle to the obex. This was based on the assumption that syringomyelic cavity in most patients communicated with the fourth ventricle through a patent obex . These obex plugging procedures were associated with a high risk of complications including bradycardia and hypotension besides a high failure rate. Hankinson (21) and later Peerless and Durward (52) advocated foramen magnum decompression with a fourth ventricle to cisterna magna drain. Bertrand (8) described subpial excision of the tonsils. Elimination of the craniospinal pressure dissociation forms the basis of most of the current surgical approaches.
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